The principal objective of this proposal is to continue to develop a highly successful referral center for children with malignant neoplastic diseases. Since 1954 Texas Children's Hospital has maintained a specialized program for the treatment of what is now the largest case registry of children with acute leukemia in this geographical area. The key to this program has been to maintain close communication with the primary family physician. The emphasis has been on ambulatory care with much of the therapy provided by the family physician whenever practical. The system provides a continuing postgraduate education for these physicians whose cooperation with the center has been exemplary. The availability of case material has made it possible to conduct a multidisciplinary research program while offering the maximal available therapy by participation in the Southwest Oncology Group. By coordination of research programs, it is possible to use the same case material for multiple investigative programs with minimal inconvenience to the patient or family. Research programs have included investigations of the etiology, pathophysiology, natural history, and clinical management of childhood leukemia and other malignant neoplasms. Participation in the Southwest Oncology Group will be continued as will independent cancer therapy studies. The relationship with the Center for Disease Control will be maintained. Support for a program to evaluate the interrelationship of the microflora with host defense mechanisms in children with acute leukemia is being developed and collaboration with the Department of Virology on "leukemia antigen" will be expanded. Numerous multidisciplinary collaborative projects have been enacted, including the development of an immuno-oncology laboratory and a relationship with NASA for scanning electron microscopy. BIBLIOGRAPHIC REFERENCE: Mukhopadhyay, N., Richie, E., Montgomery, J. R., Wilson, R., and Fernbach, D. J.: T and B cell characteristics in combined immunodeficiency. New Engl. J. Med. 291:678, September 26, 1974.